1. Field of the Invention
The present invention generally relates to an electrical cable transition, and seal for an underground well, and more particularly, to a simple and effective wellhead electrical cable penetration through the well casing which blocks fluid and pressure flow to and from the well and eliminates any cable splices in the well.
2. Description of the Related Art
In underground wells such as oil wells, the well opening is enclosed using a well casing. The well casing seals gasses and other fluids within the well from being released into the outside environment. Equipment within the well casing is often referred to as “down-hole” within the art. Electrical power is furnished to submersible pumps and other down-hole equipment through insulated electrical conductors that extend through conduit in the well casing. In order to connect the down-hole equipment to a power source outside the well, these conductors must penetrate a wellhead barrier that is sealed to a top opening of the casing. This configuration of cables and seals in the wellhead is called a “penetrator,” the purpose for which is to provide a transition zone where the cable penetrates the wellhead barrier. The penetrator seal prevents pressure, gas and other fluids from leaking both into and out of the well past the well casing. In most wellhead designs, a hanger is used within the well head to support down-hole piping and is the component through which the penetrator assembly passes. As used herein, the term hanger is considered to be a component positioned within the wellhead from which down-piping is suspended. The penetrator may pass through the hangar, or through another portion of the wellhead.
Because the down-hole equipment must be connected to an above-ground power source, a splice or other connection must be formed between cable connected to the power source and cable extending upward from the down-hole equipment. This splice has been formed below the wellhead barrier in the past, which isolates the splice from the area around the outside of the wellhead barrier which is classified as a hazardous location. It is however desirable to perform the electrical splice above the wellhead barrier. Where the splice is outside the wellhead barrier, new power and control electronics can be readily connected to the down-hole equipment. A reliable penetrator seal around electrical lines leading up from the down-hole equipment is required.
An electrical connection within the oil well pumping system with the electro-submersible or electro-progressive cavity pump, is required for its operation. A power cable of bundled electrical conductors supplies the electrical current from a workstation controller at the surface toward the pump that is located within the well. Most common is a three-phase power cable, that is to say, consisting of three strands of electrical conductors transmitting both the electrical current, and the ability to control the operation of the pump, including the speed and rotational direction, through variation of frequencies of the electrical current. In the extreme operating environment within the well casing and the outside environment, the conductive lines carry certain special protections; a galvanized steel frame that provides a mechanical protection, a lead jacket for waterproofing each line, and a rubber isolation or ethylene propylenediene EPDM (Ethylene Propylene Diene M ASTM type) to electrically isolate each copper conductor. For this reason, the penetrator must provide a hermetic seal efficient, to isolate the internal atmosphere within the well casing with the atmosphere of the surface, this is to avoid leaks and contamination to the environment.
Currently common in the industry are two types or configurations of cable to pass through the penetrator. First, a round type that positions each line to 120°, and second a flat type which configures the three drivers in a flat configuration. It should be noted that in the round cable lead the jacket is replaced by a plastic cover and additionally has a sheathing of nitrile.
According, what is needed in the art is a wellhead penetrator device that presents a reliable sealing solution and which may be quickly installed within wellhead. Time is a very expensive variable in the production of oil and other natural resources from a well. During penetrator replacement, the well production must be stopped, the above ground electrical power disconnected, and the wellhead removed while a new penetrator is installed. The installation time must be as short and efficient as possible, and the seal integrity and service life of the penetrator must be maximized. To ease the installation of the penetrator device by maintenance crews, a minimum number of components is desirable, and the penetrator design should not require the use of adhesives or sealants. The penetrator seal must also be highly reliable under varying pressures within the well casing. It is thus to such underground well electrical penetrator with floating seal that the present invention is primarily directed.